Method of operating a liquefracture handpiece

ABSTRACT

A surgical handpiece having at least two lumens or tubes mounted to a body. At least one tube is used for aspiration and at least one other tube is used to inject heated surgical fluid for liquefying a cataractous lens. A portion of the second tube is enlarged to form a pumping chamber. The pumping chamber works by boiling a small volume of the surgical fluid. As the fluid boils, it expands rapidly, thereby propelling the liquid downstream of the pumping chamber out of the second tube. The pumping chamber may use a pair of electrodes.

This application is a continuation of U.S. patent application Ser. No.09/447,752, filed Nov. 22, 1999, currently co-pending, which is acontinuation-in-part application of U.S. patent application Ser. No.09/090,433, filed Jun. 4, 1998, now U.S. Pat. No. 6,080,128, issued Jun.27, 2000.

BACKGROUND OF THE INVENTION

This invention relates generally to the field of cataract surgery andmore particularly to a pumping chamber for a handpiece for practicingthe liquefracture technique of cataract removal.

The human eye in its simplest terms functions to provide vision bytransmitting light through a clear outer portion called the cornea, andfocusing the image by way of the lens onto the retina. The quality ofthe focused image depends on many factors including the size and shapeof the eye, and the transparency of the cornea and lens.

When age or disease causes the lens to become less transparent, visiondeteriorates because of the diminished light which can be transmitted tothe retina. This deficiency in the lens of the eye is medically known asa cataract. An accepted treatment for this condition is surgical removalof the lens and replacement of the lens function by an artificialintraocular lens (IOL).

In the United States, the majority of cataractous lenses are removed bya surgical technique called phacoemulsification. During this procedure,a thin phacoemulsification cutting tip is inserted into the diseasedlens and vibrated ultrasonically. The vibrating cutting tip liquifies oremulsifies the lens so that the lens may be aspirated out of the eye.The diseased lens, once removed, is replaced by an artificial lens.

A typical ultrasonic surgical device suitable for ophthalmic proceduresconsists of an ultrasonically driven handpiece, an attached cutting tip,and irrigating sleeve and an electronic control console. The handpieceassembly is attached to the control console by an electric cable andflexible tubings. Through the electric cable, the console varies thepower level transmitted by the handpiece to the attached cutting tip andthe flexible tubings supply irrigation fluid to and draw aspirationfluid from the eye through the handpiece assembly.

The operative part of the handpiece is a centrally located, hollowresonating bar or horn directly attached to a set of piezoelectriccrystals. The crystals supply the required ultrasonic vibration neededto drive both the horn and the attached cutting tip duringphacoemulsification and are controlled by the console. The crystal/hornassembly is suspended within the hollow body or shell of the handpieceby flexible mountings. The handpiece body terminates in a reduceddiameter portion or nosecone at the body's distal end. The nosecone isexternally threaded to accept the irrigation sleeve. Likewise, the hornbore is internally threaded at its distal end to receive the externalthreads of the cutting tip. The irrigation sleeve also has an internallythreaded bore that is screwed onto the external threads of the nosecone.The cutting tip is adjusted so that the tip projects only apredetermined amount past the open end of the irrigating sleeve.Ultrasonic handpieces and cutting tips are more fully described in U.S.Pat. Nos. 3,589,363; 4,223,676; 4,246,902; 4,493,694; 4,515,583;4,589,415; 4,609,368; 4,869,715; 4,922,902; 4,989,583; 5,154,694 and5,359,996, the entire contents of which are incorporated herein byreference.

In use, the ends of the cutting tip and irrigating sleeve are insertedinto a small incision of predetermined width in the cornea, sclera, orother location. The cutting tip is ultrasonically vibrated along itslongitudinal axis within the irrigating sleeve by the crystal-drivenultrasonic horn, thereby emulsifying the selected tissue in situ. Thehollow bore of the cutting tip communicates with the bore in the hornthat in turn communicates with the aspiration line from the handpiece tothe console. A reduced pressure or vacuum source in the console draws oraspirates the emulsified tissue from the eye through the open end of thecutting tip, the cutting tip and horn bores and the aspiration line andinto a collection device. The aspiration of emulsified tissue is aidedby a saline flushing solution or irrigant that is injected into thesurgical site through the small annular gap between the inside surfaceof the irrigating sleeve and the cutting tip.

Recently, a new cataract removal technique has been developed thatinvolves the injection of hot (approximately 45° C. to 105° C.) water orsaline to liquefy or gellate the hard lens nucleus, thereby making itpossible to aspirate the liquefied lens from the eye. Aspiration isconducted with the injection of the heated solution and the injection ofa relatively cool solution, thereby quickly cooling and removing theheated solution. This technique is more fully described in U.S. Pat. No.5,616,120 (Andrew, et al.), the entire contents of which is incorporatedherein by reference. The apparatus disclosed in the publication,however, heats the solution separately from the surgical handpiece.Temperature control of the heated solution can be difficult because thefluid tubings feeding the handpiece typically are up to two meters long,and the heated solution can cool considerably as it travels down thelength of the tubing.

Therefore, a need continues to exist for a control system for a surgicalhandpiece that can heat internally the solution used to perform theliquefracture technique.

BRIEF SUMMARY OF THE INVENTION

The present invention improves upon the prior art by providing asurgical handpiece having at least two lumens or tubes mounted to abody. At least one tube is used for aspiration and at least one othertube is used to inject heated surgical fluid for liquefying acataractous lens. A portion of the second tube is enlarged to form apumping chamber. The pumping chamber works by boiling a small volume ofthe surgical fluid. As the fluid boils, it expands rapidly, therebypropelling the liquid downstream of the pumping chamber out of thesecond tube. The pumping chamber may use a pair of electrodes, at leastone of the electrodes containing a countersink.

Accordingly, one objective of the present invention is to provide asurgical handpiece having at least two tubes.

Another objective of the present invention is to provide a surgicalhandpiece having a pumping chamber with two electrodes, at least oneelectrode containing a countersink.

Another objective of the present invention is to provide a surgicalhandpiece having a device for delivering the surgical fluid through thehandpiece in pulses.

These and other advantages and objectives of the present invention willbecome apparent from the detailed description and claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front, upper left perspective view of the handpiece of thepresent invention.

FIG. 2 is a rear, upper right perspective view of the handpiece of thepresent invention.

FIG. 3 is a cross-sectional view of the handpiece of the presentinvention taken along a plane passing through the irrigation channel.

FIG. 4 is a cross-sectional view of the handpiece of the presentinvention taken along a plane passing through the aspiration channel.

FIG. 5 is an enlarged partial cross-sectional view of the handpiece ofthe present invention taken at circle 5 in FIG. 4.

FIG. 6 is an enlarged partial cross-sectional view of the handpiece ofthe present invention taken at circle 6 in FIG. 3.

FIG. 7 is an enlarged cross-sectional view of the handpiece of thepresent invention taken at circle 7 in FIGS. 3 and 4, and showing aresistive boiler pump.

FIG. 8 is an exploded, partial cross-section view of one embodiment ofthe handpiece of the present invention.

FIG. 9 is a block diagram of a control system that can be used with thehandpiece of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Handpiece 10 of the present invention generally includes handpiece body12 and operative tip 16. Body 12 generally includes external irrigationtube 18 and aspiration fitting 20. Body 12 is similar in construction towell-known in the art phacoemulsification handpieces and may be madefrom plastic, titanium or stainless steel. As best seen in FIG. 6,operative tip 16 includes tip/cap sleeve 26, needle 28 and tube 30.Sleeve 26 may be any suitable commercially available phacoemulsificationtip/cap sleeve or sleeve 26 may be incorporated into other tubes as amulti-lumen tube. Needle 28 may be any commercially available hollowphacoemulsification cutting tip, such as the TURBOSONICS tip availablefrom Alcon Laboratories, Inc., Fort Worth, Tex. Tube 30 may be anysuitably sized tube to fit within needle 28, for example 29 gaugehypodermic needle tubing.

As best seen in FIG. 5, tube 30 is free on the distal end and connectedto pumping chamber 42 on the proximal end. Tube 30 and pumping chamber42 may be sealed fluid tight by any suitable means having a relativelyhigh melting point, such as a silicone gasket, glass frit or silversolder. Fitting 44 holds tube 30 within bore 48 of aspiration horn 46.Bore 48 communicates with fitting 20, which is journaled into horn 46and sealed with O-ring seal 50 to form an aspiration pathway throughhorn 46 and out fitting 20. Horn 46 is held within body 12 by O-ringseal 56 to form irrigation tube 52 which communicates with irrigationtube 18 at port 54.

As best seen in FIG. 7, in a first embodiment of the present invention,pumping chamber 42 contains a relatively large pumping reservoir 43 thatis sealed on both ends by electrodes 45 and 47. Electrical power issupplied to electrodes 45 and 47 by insulated wires, not shown. In use,surgical fluid (e.g. saline irrigating solution) enters reservoir 43through port 55, tube 34 and check valve 53, check valves 53 beingwell-known in the art. Electrical current (preferably Radio FrequencyAlternating Current or RFAC) is delivered to and across electrodes 45and 47 because of the conductive nature of the surgical fluid. As thecurrent flows through the surgical fluid, the surgical fluid boils. Asthe surgical fluid boils, it expands rapidly out of pumping chamber 42through port 57 and into tube 30 (check valve 53 prevents the expandingfluid from entering tube 34). The expanding gas bubble pushes thesurgical fluid in tube 30 downstream of pumping chamber 42 forward.Subsequent pulses of electrical current form sequential gas bubbles thatmove surgical fluid down tube 30. The size and pressure of the fluidpulse obtained by pumping chamber 42 can be varied by varying thelength, timing and/or power of the electrical pulse sent to electrodes45 and 47 and by varying the dimensions of reservoir 43. In addition,the surgical fluid may be preheated prior to entering pumping chamber42. Preheating the surgical fluid will decrease the power required bypumping chamber 42 and/or increase the speed at which pressure pulsescan be generated.

Preferably, electrode 45 contains small depression or countersink 100having any suitable depth but approximately 0.003 inches beingpreferred. Pumping reservoir 43 is narrowest at periphery 101 (on theorder of 0.1 mm) and as a result, fluid in pumping reservoir 43 boilsfirst at periphery 101 and the steam wave front travels down countersink100 toward the central axis of tube 30. The surgical fluid conductselectricity much better in the liquid state than in the vapor state.Consequently, current flow diminishes greatly at periphery 101 whereboiling occurs first.

While several embodiments of the handpiece of the present invention aredisclosed, any handpiece producing adequate pressure pulse force, risetime and frequency may also be used. For example, any suitable handpieceproducing a pressure pulse force of between 0.03 grams and 50.0 grams(between 1 gram and 50.0 grams being preferred), with a pressure pulserise time of between 1 gram/second and 50,000 grams/second (with between500 grams/second and 50,000 grams/second being preferred) and afrequency of between 1 Hz and 200 Hz may be used, with between 10 Hz and100 Hz being most preferred. The pressure pulse force and frequency maybe varied with the hardness of the material being removed. For example,the inventors have found that a lower frequency with a higher pulseforce is more efficient at debulking and removing the relatively hardnuclear material, with a higher frequency and lower pulse force beinguseful in removing softer epinuclear and cortical material. Infusionpressure, aspiration flow rate and vacuum limit are similar to currentphacoemulsification techniques.

As seen in FIG. 9, one embodiment of control system 300 for use inoperating handpiece 310 includes control module 347, RF amplifier 312and function generator 314. Power is supplied to RF amplifier 312 by DCpower supply 316, which preferably is an isolated DC power supplyoperating at ±200 volts. Control module 347 may be any suitablemicroprocessor, and may receive input from operator input device 318.Function generator 314 provides the electric wave form to amplifier 312and preferably operates at 450 KHz to help minimize corrosion.

In use, control module 347 receives input from surgical console 320.Console 320 may be any commercially available surgical control consolesuch as the LEGACY® SERIES TWENTY THOUSAND® surgical system availablefrom Alcon Laboratories, Inc., Fort Worth, Tex. Console 320 is connectedto handpiece 310 through irrigation line 322 and aspiration line 324,and the flow through lines 322 and 324 is controlled by the user viafootswitch 326. Irrigation and aspiration flow rate information inhandpiece 310 is provided to control module 347 by console 320 viainterface 328, which may be connected to the ultrasound handpiececontrol port on console 320 or to any other output port. Control module347 uses footswitch 326 information provided by console 320 and operatorinput from input device 318 to generate two control signals 330 and 332.Signal 332 is used to operate pinch valve 334, which controls thesurgical fluid flowing from fluid source 336 to handpiece 310. Fluidfrom fluid source 336 is heated in the manner described herein. Signal330 is used to control function generator 314. Based on signal 330,function generator 314 provides a wave form at the operator selectedfrequency and amplitude determined by the position of footswitch 326 toRF amplifier 312 which is amplified to advance the powered wave form tohandpiece 310 to create heated, pressurized pulses of surgical fluid.

As best seen in FIGS. 3, 4 and 7, surgical fluid may be supplied topumping chamber 43 through tube 34 or, as seen in FIG. 8, surgical fluidmay be supplied to pumping chamber 243 through irrigation fluid tube 234which branches off main irrigation tube 235 supplying cool surgicalfluid to the operative site. As seen in FIG. 8, aspiration tube 237 maybe contained internally to handpiece 10.

Any of a number of methods can be employed to order limit the amount ofheat introduced into the eye. For example, the pulse train duty cycle ofthe heated solution can be varied so that the total amount of heatedsolution introduced into the eye does not vary with the pulse frequency.Alternatively, the aspiration flow rate can be varied as a function ofpulse frequency so that as pulse frequency increases aspiration flowrate increases proportionally.

This description is given for purposes of illustration and explanation.It will be apparent to those skilled in the relevant art that changesand modifications may be made to the invention described above withoutdeparting from its scope or spirit. For example, it will be recognizedby those skilled in the art that the present invention may be combinedwith ultrasonic and/or rotating cutting tips to enhance performance.

We claim:
 1. A method of operating a liquefracture handpiece, thehandpiece having a body and a pumping chamber contained within the body,the method comprising the steps of: a) operating the pumping chamber ata pulse frequency to produce a pressure pulse having a pressure pulseforce of between 0.03 grams and 50.0 grams; b) varying the pulsefrequency; and c) varying an aspiration flow rate as a function of thepulse frequency.
 2. The method of claim 1 wherein the pressure pulseforce has a rise time of between 1 gram/second and 50,000 grams/second.3. A method of operating a liquefracture handpiece, the handpiece havinga body and a pumping chamber contained within the body, the methodcomprising the steps of: a) operating the pumping chamber at a pulsefrequency and with a pulse train duty cycle to produce a pressure pulsehaving a pressure pulse force of between 0.03 grams and 50.0 grams; b)varying the pulse frequency; and c) varying the pulse train duty cycleas a function of the pulse frequency.
 4. The method of claim 3 whereinthe pressure pulse force has a rise time of between 1 gram/second and50,000 grams/second.
 5. A method of operating a liquefracture handpiece,the handpiece having a body and a pumping chamber contained within thebody, the method comprising the steps of: a) operating the pumpingchamber at a predetermined operating parameter so as to produce a pulsestream of pressure pulses, the pressure pulses having a pressure pulseforce of between 0.03 grams and 50.0 grams; and b) varying the operatingparameter so as to vary the coherence length of the pulse stream.
 6. Themethod of claim 5 wherein the pressure pulse force has a rise time ofbetween 1 gram/second and 50,000 grams/second.
 7. The method of claim 5wherein the parameter is flow development.
 8. The method of claim 5wherein the parameter is pressure.
 9. The method of claim 5 wherein theparameter is temperature.
 10. A method of operating a liquefracturehandpiece, the handpiece having a body and a pumping chamber containedwithin the body, the method comprising the steps of: a) operating thepumping chamber at a pulse frequency to produce a plurality of pressurepulses having a rise time of between 1 gram/second and 50,000grams/second; b) varying the pulse frequency; and c) varying anaspiration flow rate as a function of the pulse frequency.
 11. A methodof operating a liquefracture handpiece, the handpiece having a body anda pumping chamber contained within the body, the method comprising thesteps of: a) operating the pumping chamber at a pulse frequency and witha pulse train duty cycle to produce a plurality of pressure pulseshaving a rise time of between 1 gram/second and 50,000 grams/second; b)varying the pulse frequency; and c) varying the pulse train duty cycleas a function of the pulse frequency.
 12. A method of operating aliquefracture handpiece, the handpiece having a body and a pumpingchamber contained within the body, the method comprising the steps of:a) operating the pumping chamber at a predetermined operating parameterso as to produce a pulse stream of pressure pulses, the pressure pulseshaving a rise time of between 1 gram/second and 50,000 grams/second; andb) varying the operating parameter so as to vary the coherence length ofthe pulse stream.
 13. The method of claim 12 wherein the parameter isflow development.
 14. The method of claim 12 wherein the parameter ispressure.
 15. The method of claim 12 wherein the parameter istemperature.